Truly a bizzaro day for the west coast yesterday. The imagery and animations below tell the story but first some background

It began with an upper high pressure that had brought warm weather to California for days. Finally, yesterday the clockwise spinning winds of the upper high pressure moved into Canada.

At the same counter-clockwise spinning Cut-Off Low retrograded (went from East to West and came over the Bay Area at dawn yesterday. This made for strong North then West winds over the Bay Area. Then in the afternoon the upper Cut-Off Low went over the ocean where it induced a counter-clockwise spinning surface low pressure just north of the Golden Gate. This created created a marine surge as foggy air shot up the coast from Southern California as saw at the Golden Gate. The combo of marine surge winds, strong W winds aloft and southerly winds from the spinning low pressure created winds over 30 knots at sites that are open more southerly wind.

Now take a look the annotated imagery at the below to see this pattern unfold.

Then in the first animation at the bottom watch the upper level winds of the Cut-Off Low. Notice how the wind focus for WEST winds is at Crissy while the focus of EAST winds is in the Gorge.

The second animation is puzzling at first since it shows the surface isobars. The Cut-Off Low does not show since it is up at 18K feet. But as it slides across California you will see a surface low pressure with counter-clockwise spinning winds blossom off the Bay Area.

And what did these systems do to Southern California? Strong Catalina Eddy southerly winds and deep marine layer clouds!

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